Field of the Invention
The present invention relates to a positioning system and method and, more particularly, to the positioning system and method that precisely obtain a target position using the time difference of receiving and sending information.
Description of the Related Art
Positioning systems are mainly divided into the following four types: a triangulation positioning system, a proximity positioning system, a scene analysis positioning system, and a mixed positioning system. For the triangulation positioning system, refer to U.S. Pat. No. 5,646,632 entitled “Method and apparatus for a portable device to identify its own location” and U.S. Pat. No. 6,275,705 entitled “Location and tracking system”. Both patents use the characteristics of a distance or an angle between a base station or a sensor and a user for the positioning purpose. If a distance is used, the time for a signal transmission or the degree of signal attenuation will be used for computation. If an angle is used, an included angle between two reference points will be used for determining a position, and the angle may be obtained from a specially designed hardware device.
With reference to P.R.C. Pat. No. 104270710 entitled “A Bluetooth indoor positioning system based on iBeacon”, iBeacons are used to construct a wireless sensor network, and each iBeacon acts as a beacon node. A RSSI algorithm is used to measure the distance from an unknown node to a plurality of beacon nodes, and triangulation and maximum likelihood algorithms are used for the Bluetooth positioning system for the comprehensive evaluation of the location of the finally confirmed unknown node. However, the accuracy of the RSSI algorithm may be affected and interfered by the environment easily, so that the positioning precision is not accurate enough and so that the valid range is limited. On the other hand, the positioning technology of the triangulation algorithm has a common characteristic of requiring at least two or three base stations to determine an object's position and a relatively more complicated system layout.
For the proximity positioning system, refer to U.S. Pat. No. 5,493,283 entitled “Locating and authentication system”. The range of coverage of a base station or a sensor must be changed according to the required positioning precision. If the required precision is high, the range of coverage has to be small. The number of base stations or sensors will be large, and the construction cost will be very expensive.
For the scene analysis positioning system, refer to U.S. Pat. No. 6,839,027 entitled “Location measurement process for radio-frequency badges employing path constrains”. The process requires specific databases built for different environments respectively, so that the configuration is more complicated. The signal intensity of several wireless network base stations in the environment is used to determine the location of a user, thus requiring the measurement of a signal intensity of different positions in advance in order to build the database of the signal intensities at different positions. Then, the currently measured signal intensity is used to further obtain the most probable position.
For the mixed positioning system, refer to R.O.C. Pat. No. 1432761 entitled “Position detecting method and system, and distance measuring method”. The system comprises a plurality of signal transmission devices, a wireless coordination device, and a plurality of sensing apparatuses. The sensing apparatus includes a wireless sensing device, and a timer is started when the signal transmission device receives a radio frequency signal. When the signal transmission device receives an ultrasonic signal, the time difference of receiving the radio frequency signal and the ultrasonic signal is used to estimate and obtain a measured distance value of the distance of the signal transmission device. However, this system requires a plurality of signal transmission devices, and a plurality of sensing apparatuses, so that it results in a high construction cost.
Refer to U.S. Pat. No. 6,865,347 entitled “Optically-based location system and method for determining a location at a structure”. A camera device and specially designed hardware are used to measure the azimuth, the angle of elevation, and the distance of an incident light. However, the result of this method may be affected by sunlight or other light sources, so that its practicability is low.
Refer to R.O.C. Pat. No. 1398180 entitled “Actor assisted enhanced positioning method”. An upstream signal of a first UE and at least one second UE is received and marked, and a downstream signal at the first UE and coming from at least one base station is received and marked. The time labels are used to determine the time difference of the observed arrivals. The position of the first UE is determined by the determined arrival time difference. However, the time difference of this patented technology is determined by an elliptical area of several base stations.
Refer to R.O.C. Pat. Appln. No. 103119118 entitled “Positioning system, positioning method, and positioning program”. The information of a plurality of signal sources and the received record of a plurality of non-audible sounds in a mobile terminal are used for the positioning purpose. However, this technology requires the plurality of signal sources and the plurality of non-audible sounds, thus incurring complicated construction and high cost.
In view of the aforementioned problems, a feasible solution is provided to overcome the problems of the prior art.